The present invention relates to the so-called BiCMOS integrated circuit device having both bipolar transistors and metal-oxide-semiconductor field effect transistors (hereinafter referred to as "MOS transistor(s)") on the same semiconductor substrate and, more particularly, to those in which their characteristic features reside in an output circuit for performing a level shifting operation directly with respect to an external circuit.
In a typical conventional output circuit of a BiCMOS integrated circuit device, there are two bipolar transistors or a pair of CMOS (complementary MOS) transistors which constitute an output circuit having a push-pull configuration. The integrated circuit device having an output circuit consisting of two bipolar transistors can readily be connected to or disconnected from a bus line of an active state, to which a plurality of integrated circuit device are connected. However, the above circuit device has a defect in that the circuit construction is inevitably complicated. The reason for this is explained in detail later. Although, on the other hand, the integrated circuit device having an output circuit consisting of a pair of CMOS transistors can be organized to have a simpler construction as compared to that composed of the bipolar transistors, it cannot be connected to or disconnected from an active bus line easily.